In order to write data to media, a write head is typically used. Such a write head is generally part of a merged head that includes a head for writing and a head for reading data from the media. FIG. 1 depicts a side view of a portion of a conventional write head 10. The conventional write head 10 includes a conventional first pole (P1) 12 having a conventional pedestal 14, a conventional write coil 20, a conventional second pole (P2) 30 and a conventional write gap 40 separating the conventional P1 12 from the conventional P2 30. The conventional pedestal 14 and the conventional P2 30 include high saturation magnetization layers 16 and 32, respectively. The conventional write head 10 also includes an insulating layer 22 used to insulate coils 20. The insulating layer 22 is typically a hardbaked photoresist layer. A conventional thermal actuation coil 60 used in actuating the pole tip of the conventional write head 10 is also provided.
In operation the conventional write head 10 is actuated. Stated differently, the fly height, h, of the conventional write head 10 above the air bearing surface (ABS) is controlled. Many conventional mechanisms of actuating the conventional write head 10 exist. For example, the slider on which the conventional write head 10 resides is typically actuated. Other conventional mechanisms of actuation for the write head 100, such as those based on electrostatic or aerodynamics exists. In addition or in lieu of at least some of these mechanisms, the pole tip 50 may be actuated. In the conventional write head 10 shown, the pole tip 50 is thermally actuated. The conventional write head 10 is thus analogous to the system described in U.S. Pat. No. 5,991,113. During writing, a current is driven through the conventional thermal actuation coil 60, which is embedded in the insulating overcoat above the P2 30. This current heats the conventional write head 10. In particular, the overcoat above is heated and, therefore, expands. During expansion, the overcoat draws a portion of the conventional P2 with it, allowing the conventional pole tip 50 to protrude. As a result, the pole tip 50 is actuated, moving closer to the ABS and reducing the fly height in the localized region around the pole tip 50.
Although the conventional write head 10 allows for the pole tip 50 to be thermally actuated, one of ordinary skill in the art will readily recognize that there are drawbacks to use of the conventional write head 10. In order to sufficiently heat the overcoat, the current driven through the conventional thermal actuation coil 60 is quite large, often on the order of a few hundred mA. Driving such a large current consumes a significant amount of power. Such a large current not only heats the overcoat, but may also significantly heat a read sensor (not shown) associated with the conventional write head. This heating can cause failures not only in the overcoat, but also in the read sensor. Furthermore, because of such heating, the bias current driven through the read sensor during reading may have to be reduced, resulting in a loss of signal. Thermal actuation also takes a significant amount of time because both energizing the coil 60 with a sufficient current and sufficient heating of the overcoat are required. Consequently, thermal actuation is relatively slow, approximately in the millisecond regime. Moreover, the expansion of the overcoat occurs primarily above the thermal actuation coil 60. Thus, thermal actuation may be less effective in moving the pole tip 50 closer to the ABS. Stated differently, the amount that the fly height can be adjusted using thermal actuation of the pole tip 50 may be relatively limited.
Accordingly, what is needed is a system and method for improving dynamic actuation of the write head during operation. The present invention addresses such a need.